Container closures or caps are generally lined with a thin metal foil or paper liner before assembly onto the container. There are many types of machines for applying the liners to the caps. Most operate by feeding a cap into a cap-lining mechanism where a paper insert is punched from a web of liner paper and then tamped into the cap. Most machines line an extraordinary quantity of caps at an incredible rate. The machines often fail, however, creating downtime that can result in production and supply issues.
In many past cap-lining machines, the caps were mechanically fed into the cap-lining machine, such as by a stuffer rod which pushed a set of caps into a channel toward the machine. A line of caps thus moved through the channel, the stuffer rod pushing the line forward and sequentially adding an incoming set of caps at the upstream end while downstream caps moved off the line and into the cap-lining mechanism. These stuffer rods were frequently used in tracks which included a right-angle bend, and were limited in that the stuffer rods could only advance a set of caps when the caps were fed to the stuffer rods; the speed with which the stuffer rod could push caps down the track was inversely proportional to the number of caps to be fed to the stuffer rod. Beyond these inefficiencies, there were a number of ways that past cap-lining machines failed. For instance, if the supply of caps to the cap-lining mechanism ceased, the cap-lining mechanism would still continue to punch and tamp—and thus waste—liner inserts. If it was successfully detected, a problem such as this required shutting down the entire machine, fixing the cap supply problem, removing jammed liner inserts, resetting the paper liner feed, and restarting the machine, resulting in considerable lost time and production. Numerous attempts at solving the liner paper waste problem were made, most focusing on stopping the feeding of the liner paper when the cap supply ceased.
New cap construction techniques, however, render many of these past machines undesirable. Cap manufacturers are using increasingly softer and lighter materials to create thinner, more pliable caps. When such caps are advanced through a narrow channel, as by the stuffer rod, they frequently deform and bind within the channel. The caps may be permanently deformed, in which case the liner inserts cannot be properly applied to the caps, or the caps may actually crack, in which case the liner insert can be applied but will not form a heat seal when the cap is assembled on the closure. When a cap binds within the channel, the downstream caps fail to advance, and the upstream caps become jammed, deformed, and broken as more caps are stuffed down the channel by the stuffer rod. While the cap-lining machine may detect that a new cap has not been presented to the cap-lining mechanism, upstream caps may continue to be damaged, and a worker must shut the machine down, remove the bound cap, inspect the machine for damage, inspect and remove the damaged caps from the system, and restart the machine.
The new construction of caps presents problems for holding the caps in position in preparation for lining as well. In the past, caps were placed under the punch or tamper and held in alignment with the tamper by a biased or sprung mechanism acting on the cap from one or several sides. After the cap had been lined, the cap would be advanced from the biased mechanism. The caps frequently squeezed out of the biased mechanism at high speeds, which could cause the caps to fly out of the machine, move too quickly for downstream daisy-chained operations, or jam in the downstream channel. Further, the biased mechanism could deform or even crush the cap while it was being held in place for lining. This would result in an improperly-fit liner insert, caps moved out of alignment from the punch, smashed caps, jammed lining locations, and other problems which caused mechanical damage to the cap-lining machine and could require the cap-lining machine to be shut down and repaired.
The past machines were also dangerous to users. Most of the mechanical assemblies that would stop the feed of the liner paper when a cap was missing used heavy, complex, moving parts. Machines that mechanically moved caps into place, such as by large rotating tables, cam-driven racks, or stuffer rods, usually employed heavy, rugged, metal fixtures. The stuffer rods, for instance, were frequently driven by clutched gear assemblies capable of producing a large amount of torque and force to push a long line of caps toward and through a cap-lining machine. Moving parts such as these presented safety hazards to errant fingers and limbs.